Electrolytes and method for electroplating nickel



United St tes Patent ABSTRACT OF THE DISCLOSURE In accordance with certain of its aspects,'this invention relates to novel compositions and to a process for electroplating nickel onto a basis metal which comprises passing current from an anode to a basis metal cathode through an aqueous acidic nickel plating solution containing at least one nickel compound providing nickel ions for electroplating nickel, a primary brightener, and as a second ary brightener a compound containing an-anion of the structure:

carbon-di-yl moiety which contains at least. 2 carbon atoms.

This invention relates to electroplating nickel and more particularly to the electrodeposition of bright nickel.

Nickel electrodeposits may be plated from various types of plating baths including Watts-type baths, high-chloridetype baths, sulfamate-type baths, fluoroborate-type baths, etc. As is well known to those skilled-in-the-art, deposition of satisfactory bright nickel plate from such baths requires the presence of various additives- The main additives commonly employed are those identified as primary brighteners and secondary brighteners. Secondary brighteners, as this term is commonly employed, refers to additives used in relatively highconcentrations, which permit attainment of a semi-bright and somewhat lustrous deposit. The result so attained is typically modified to produce a mirror bright, highly lustrous,. leveled, and finegrained deposit by the further addition to the bath of components commonly identified as primary brighteners. In order to obtain enhanced rates of brightening. and leveling with certain combinations of primary andsecondary brighteners, a third class of additives identified as secondary auxiliary additives may be used.

Although many compositions have been heretofore tried for the use as secondary brightening agents, it has been found that there are very few secondary brighteners which are completely satisfactory. As is well known, commonly available secondary brighteners areless than fully desirable in that they may have one or more of the defects herein noted. Typically, prior art secondary brighteners do not eifectively cooperate with many of the primary brighteners and secondary auxiliary brighteners which are commonly used; and they do not permit attainment of the maximum luster, bright plate range, leveling, deposit ductility, freedom from haze, etc, Furthermore,-many of the prior art secondary brighteners possess little or no surface activity and accordingly, the nickel deposited may have a tendency toward gas-pitting. It is also a particular defect of many prior art secondary brighteners that they possess little or no tolerance to metallic inpurities which may commonly be introduced into a nickel plating bath. Most commonly, the prior art secondary brighteners are 3,399,123 Patented Aug. 27, 1968 highly intolerant to the presence of zinc; in fact, relatively low concentrations of zinc introduced into the bath may render the bath substantially inoperative.

In addition, many of the prior art secondary brighteners may'not give satisfactory deposits in the high chloride containing baths, i.e. baths containing nickel chloride contents in amounts greater than about grams per liter. These prior art secondary brighteners, in high chloride baths, either fail to give bright deposits over a sufiiciently wide current density range or result in poor deposit'ductility.

It is a further characteristic of secondary brighteners heretofore employed that some of them may be hydrolyzed, reduced, etc., at an economically unsatisfactory rate when used under normal conditions of nickel plating, thus requiring frequent replenishment. The resulting decomposition products which build up in the baths over extended periods of operation may be extremely harmful. Specifically, the hydrolysis and/or other degradation products may adversely effect properties of the nickel plate such as ductility, leveling, internal stress, etc.

It is an object of this invention to provide an improved nickel plating process characterized by the use of a new class of superior secondary brightener. It is a further object of this invention to provide bath compositions for nickel plating from which bright nickel electrodeposits may be obtained. Another object of this invention is to provide novel compositions which may be used as secondary brighteners in bright nickel plating baths and processes for preparing these nickel plating compositions. Other objects of this invention may be apparent to those skilledin-the-art on inspection of the following description.

In accordance with certain of its aspects, the process of this invention comprises electrodepositing nickel from an aqueous nickel electroplating bath containing at least one compound providing nickel ions, a primary brightener, and as a secondary brightener a composition having an anion [R-S O3 ]uH1n SO N [-R-'SO3 ]b l-b (I) wherein a and b may each be integers 01 and R may be a hydrocarbon-di-yl moiety which contains at least 2 carbon atoms.

The basis metal onto which bright deposits may be plated by the process of this invention may include ferrous metals such as steels; copper, including its alloys such as brass, bronze, etc; zinc particularly in the for of die castings which may bear a plate of copper; etc. Typically such basis metal may bear a first plate of copper and/or a plate of semi-bright nickel.

The novel baths of this invention may typically include Watts-type baths, sulfarnate-type baths, fluoborate-type baths, chloride-free sulfate baths, chloride-free sulfamate baths, high chloride baths, etc.

A typical Watts bath which may be used in practice of this invention may include the following components in aqueous solution, all values being in grams per liter (g./l.) except for the pH:

A typical sulfamate-type bath which may be used in practice of this invention may include the following components:

A typical fiuoborate-type bath which may be used in practice of this invention may include the following components:

TABLE III Component Minimum Maximum Preferred Nickel fluoboratc 250 400 300 Nickel chloride hydrated 15 60 30 Boric acid 15 30 20 pH clectrometric. 3 4 3. 5

A typical chloride-free sulfate-type bath which may be used in practice of this invention may include the following components:

TABLE IV Component Minimum Maximum Preferred Nickel sulfate hydrated... 300 500 400 Boric acid 35 55 45 pH clectrornetric. 3 5 4.

A typical chloride-free sulfamate bath which may be used in practice of this invention may include the following components:

TABLE V Component Minimum Maximum Preferred Nickel sulfamate 300 400 350 Boric acid 35 55 45 pH electrometric 3 4 Typical high chloride baths which may be used to obtain higher plating speeds in practice of this invention may include the following components:

TABLE VI Component Minimum Maximum Preferred Nickel chloride hydrated 80 300 250 Nickel sulfate hydrated 40 250 250 Boric acid 35 55 45 pH electrometric 3 5 4. 0

It may be noted that nickel sulfate hydrated normally corresponds to the heptahydrate and nickel chloride hydrated normally corresponds to the hexahydrate, although nickel chloride may also be available as an aqueous concentrate or as the dihydrate. In the above tables, nickel sulfate hydrated represents the heptahydrate and nickel chloride hydrated represents the hexahydrate.

It will be apparent to those skilled in the art that the above baths may contain components in amounts falling outside the preferred minima and maxima set forth, but most satisfactory and economical operation may n0rmally be effectedv when the components are :present in the quantities indicated.

It will be further apparent that the baths in order to obtain bright, leveled, and ductile deposits will contain primary brighteners, as are known in the art, e.g. acetylenic, N-heterocyclic, active sulfur, etc. primary brighteners.

Other cooperating additives which give desired effects may also be present. These include secondary auxiliary brighteners e.g. sodium allyl sulfonate, sodium 3-chloro-2- butene sulfonate-l etc., anti-pitting agents such as sodium lauryl sulfonate, sodium lauryl ether sulfate, sodium din-hexyl sulfosuccinate, etc.; and other secondary brighteners such as saccharin(o-benzoic sulfimide), dibenzene sulfonimide etc. These cooperating additives may be carefully correlated with the secondary brighteners of this invention as to compatibility, concentration etc. to obtain optimum results with respect to deposit brilliance, bright plate current density range, ductility, leveling, low our- 4 rent density'coverage, tolerance to metallic and organic impurities, etc.

It has been found, in particular, that when the secondary brighteners of this invention are used together with low concentrations-of zinc-intolerant secondary brighteners, the baths may be zinc tolerant, and beneficial synergistic effects in leveling and rate of brightening may be attained.

Furthermore, it has been found that when the secondary brighteners of this invention are employed in high chloride baths also containing primary brighteners, an unexpectedly wide bright plate current density range and good deposit ductility may be attained. Particularly wide bright plate current density range and good deposit ductility may be observed when such high chloride baths also contain an additional secondary brightener such as a from zene sulfonate or a benzene sulfonarnide.

The novel secondary brightener compounds which may be used in practice of the process of this invention may be compounds which in aqueous solution yield the anion [RSOalbHi-b (11) wherein a and b may each be integers 0-1 and R may be a hydrocarbon-di-yl moiety which contains at least 2 carbon atoms.

Preferably the hydrocarbon-di-yl moiety R may be an alkane-di yl moiety including ethane-di-yl, propane-di-yl, butane-di-yl, pentane-di-yl, hexane-di-yl, etc; an arylene moiety including phenylene, etc.; an alkarylene moiety including methyl phenylenes such as 1- methyl-2,3-phenylone; l-ethyl-3,4-phenylene; l-butyl 3,4 phenylene; an aralkylene moiety including phenyl ethylene, tolyl ethylene, etc. R may contain inert substituents including e.g. alkyl, aryl, halogen, etc.

Preferably R may be a polymethylene group (CH wherein It may be an integer of at least 2 and preferably 2-5. In this event, the anion (I) may be:

COO 2) n-SOa [(CHz) SOs-RE (III) In a preferred embodiment of the invention, wherein n is 3, the anion may be:

0 O 0 line-S03 It will be apparent that when a and b are each 0, the anion (1) maybe:

When one of a and b is l, the anion (I) may be:

When a and b are each 1, the anion (I) may be:

C O O-R-S 03' S Or-N R-S 03' (VII) The preferred embodiment may be:

C OO(CH2)3SO2 SO 2-NH2 (VIII) Typically these anions may be added to the baths of this invention in the formof their bath compatible compounds Typical preferred specific compounds which may be used in practice of this invention may include:

TABLE VII Sodium 3-sulfopropyl-ortho-sulfonamidobenzoate Potassium 3-sulfopropyl-ortho-sulfonamidobenzoate Sodium 3-sulfopropyl-ortho-[N-(sodium 3-,sulfopropyl)] sulfonimidobenzoate Potassium 3-sulfopropyl-ortho-[N-(potassium 3-sulfopropyl) ]sulfonimidobenzoate Sodium 3-sulfopropyl-ortho-[N,N-(sodium 3-sulfopropyl) ]sulfona rnidobenzoate Potassium 3-sulfopropyl-ortho-[N,N-(potassium 3-sulfopropyl) ]sulfonamidobenzoate Nickel bis(3-sulfopropyl-ortho-sulfonamidobenzoate) Sodium 4-sulfobutyl-orthosulfonamidobenzoate The most preferred compounds may typically be those in which the ortho-sulfonamidobenzoate contains one sulfohydrocarbon-di-yl substituent and most preferably the first two compounds disclosed in Table VII. It will be apparent that other cations may replace those present in the specific compounds in Table VII.

The novel compounds of this invention, in accordance with certain of its aspects may be prepared by reacting in a solvent dispersion ortho-sufonamidobenzoic acid, an alkaline compound which provides the cation M in the reaction system, and a sultone. The molar ratio of orthosulfonamidobenzoic acid tov the compound which provides the cation M and to the sultone may be about 1: l: 1, 1:212, or 1:3:3 in order to obtain compounds containing respectively one, two, and three, sulfohydrocarbon-di-yl substituents. The preferred ratio may be about 1:1:1. Small molar excess amounts (about 5%) of the alkaline compound and the sultone may preferably be added and the reaction mixture may be maintained alkaline if required by further small additions of the alkaline compound.

The solvents used in this preparation may preferably be those in which the reactants are dispersible, i.e. suspendable or soluble and most preferably one in which the compound which provides the cation M is soluble. Such solvents may typically include organic solvents such as alcohols, etc.

The ortho-sulfonamidobenzoic acids which may be employed in the reaction may be represented by the formula:

COOH

(XII) A method which may be used in preparing the orthosulfonamidobenzoic acid is the hydrolysis of saccharin in strongly alkaline aqueous media by heating to form the alkali metal (such as K or Na) salt of orthosulfonamidobenzoic acid. On acidification of the reaction solution (with HCl for example) the free carboxylic acid precipitates out of solution quantitatively due to its lim ited water solubility. It can then be isolated by filtration, washing with minimum amounts of distilled water, and drying.

It may also be possible to synthesize orthosulfonamidobenzoic acid by the oxidation of o-toluene sufonamide under conditions controlled to prevent ring closure.

The alkaline compound which provides the cation M may be indicated as MX in which X is an anion and typically hydroxide OH. The preferred hydroxides may be those in which the cation is compatible with a nickel electroplating bath. Preferred examples of such compounds may be the alkali metal hydroxides, e.g. sodium hydroxide or potassium hydroxide.

When preparing salts of the sulfoalkyl-orthosulfonamidobenzoates wherein M is not an alkali metal and particularly wherein M is polyvalent, it may be desirable to first prepare the alkali metal salt and then react this salt with a cationic exchange resin on the hydrogen cycle to obtain the free sulfonic acid group or groups in the eluate. This may be reacted with the oxide, hydroxide, carbonate, etc. of the metal desired, e.g. nickel or cobalt, to form the desired metal salt of the sulfonic acid.

The sultones which may be employed to prepare the novel compounds of this invention may include those containing a carbon-oxygen-sulfur-carbon linkage in a ring, the hexavalent sulfur atom being further bonded to two additional oxygen atoms, and may be represented by the general formula:

Sago

also may produce highly useful additives. The longer chain alkane sultones or other sultones containing more than 5 carbon atoms, such as tolyl sultone,

0 s0 (XVIII) may be also used to produce additives within the scope of the invention.

When compounds of the invention are prepared with the reactants indicated above present in a molar ratio of about 1:1:1, the reaction may be indicated as follows:

When about twice as much MX and sultone as orthosulfonamidobenzoic acid on a molar basis are present, the reaction may be indicated as follows:

COOH ZMX 2 S0 R-SOsM ZHX S O N When about three times as much MX and sultone as orthosulfonamidobenzoic acid on a molar basis are present, the reaction may be indicated as follows:

C 0 O-R-SOsM From the foregoing it becomes apparent that the basic R chain (at least 2 carbon atoms, and preferably 2-5 carbon atoms) in the structure of the sulfohydrocarbon-di-yl-ortho-sulfonamidobenzoates is derived from the sultone by opening of the ring. Illustrative hydrocarbondi-yl groups may include arylene such as o-phenylene; rn-phenylene; p-phenylene; aralkylene such as o-benzyl; m-benzyl; p-benzyl; alkarylene such as 1-methyl-2,3- phenylene; l-methyl-2,4-phenylene; 1-methyl-2,5-phenylene; alkylene such as ethane-1,2-di-yl; propane-1,2-di-yl; propane-1,3-di-yl; propane-1,1,3(trimethyl)-di-yl; butan e- 1,4-di-yl; butane-1,3-di-yl; pentane-1,5-di-yl. These groups may bear inert substituenlts including hydrocarbon substituents.

The orthosulfonamidobenzoic acids which maybe used may include inert substituents on the benizene ring, e.g.

alkyl, halogen, etc., in order to obtain the sulfohydrocarbon-di-yl derivative which bear the same substituents. Such substituted derivatives may be included within the scope of this invention.

In a preferred embodiment of the invention, the orthosulfonamidobenzoic acid may be reacted under reflux in solvent, preferably methanol, with the compound MOH, preferably potassium hydroxide, in about a 1:1, 1:2, 1:3 mole ratio and with the sultone preferably 1,3-propane sultone, in a 1:1, 1:2, 1:3 mole ratio depending on wherther the mono-, di, or tri-substituted product is desired. In practice it may be preferable to use MOH and the sultone in slight (up to 5%) excess of the theoretical mole ratio to assure more complete reaction. It also may be desirable to keep the reaction mixture alkaline by further addition of MOH during the reflux period, using litmus or other suitable indicator of alkalinity. The slight excess of MOH and the sultone may result in the formation of a small amount of a hydroxy sulfonate compound which need not be separated from the desired product since such a compound is essentially inert when present in a nickel plating bath.

To obtain as high a yield of product as possible it may be preferable to evolve the solvent such as methanol by heating under reduced pressure. The essentially solventfree residue, or low solvent concentration residue, may be taken up in water, treated with a small quantity of activated carbon, filtered and diluted to a convenient stock concentration (such as g./l.) for use as a secondary brightener nickel plating additive.

The product may also be separated from the solvent by the common spray drying technique wherein the reaction mixture is sprayed into contact with hot air or a fluidized bed of the reaction product as independently produced to evolve the solvent and give a residue of dried product.

The novel compounds of this invention may also be prepared by reacting o-sulfonamidobenzoic acid with a hydroxy sulfonate,

HORSO M (XIX) by the following general reaction:

00011 HO-R-SthM SO NHz COO-R-SO3M wherein R, M, a, and b are so previously defined. For example, HORS0 M may be sodium isethionate,

H0(CH S0 Na (XX) or sodium hydroxy propane sulfonate HO(CH SO Na (XXI) In a typical example of this reaction one mole of orthosulfonamidobenzoic acid and a slight excess over two moles of sodium isethionate may be heated lfilSt in solvent medium, typically water, prefreably in the presence of a catalytic amount of a catalyst, typically boric acid, and then heated further after volatilization of the solvent to say 200 C., thereby obtaining molten sodium 3-sulfoethyl-ortho-[N-(sodium 3-sulfoethyl)] sulfonamid obenzoate,

C O O-(CHz) 2SOsNa H (XXII) The product may solidify on cooling to say 130 C. Both of the hydrogens of the sulfonamido group of the benzoic acid may enter into reaction with the hydroxy sulfonate by increasing the molar ratio of hydroxy sulfonate to benzoic acid to about 3:1. Similarly, substitution of hydrogen of the benzoic acid may be limited to the carboxyl group, with hydrogen atoms of the sulfonamido group remaining unreacted by employing about an equimolar ratio of hydroxy sulfonate to the benzoic acid.

The novel compounds or additives of this invention may preferably be used in nickel plating baths, such as those of Tables I-VI in amounts of at least 1 g./l. Lower concentrations may give appreciable grain refinement but the deposits may be less glossy. When the concentration of additive exceeds 10 g./l. the results obtained generally do not give additional advantages over the lower concentration ranges. The preferred concentration ranges from about 2-6 g./l. and most preferably 4 g./l. of additive in the plating bath.

The presence of at least one sulfohydrocarbon-di-yl group in the additives for the plating baths which may be used in this invention results in secondary brighteners which cooperate excellently with primary and secondary auxiliary brighteners in order to obtain greater luster, removal of haze, low current density coverage, uniformity, leveling, metallic impurity tolerance, and ductility than was possible with prior art secondary brighteners such as saccharin, sodium benzene monosulfonate, benzene sulfonamide, m-benzene disulfonamide, naphthalene-1,3,6- trisulfonate (sodium salt), o-sulfobenzaldehyde (sodium salt), etc. Furthermore, the sulfohydrocarbon-di-yl group imparts some surface activity to the compounds and reduces gas pitting. Moreover, the additives of the invention possess additional advantages over prior art secondary brighteners in that they render the baths highly tolerant to metallic impurities such as zinc (particularly the additives containing one or two sulfohydrocarbon-di-yl groups), and do not form harmful decomposition products over long periods of electrolysis.

Nickel plating may be carried out in accordance with certain aspects of this invention by immersing a basis metal cathode in a nickel plating bath containing the novel additive with cooperating additives as hereinbefore discussed. The anode which is also immersed in the bath may be a soluble anode, typically nickel, or an insoluble anode, typically lead. When lead is employed as anode, the plating bath may preferably be free of chloride, fluoborate, and sulfamate anions. If nickel is used as the anode, it is preferably SD type of nickel which is an electrolytic nickel containing a controlled amount of sulfur.

Plating may be carried out for a sufficient length of time to give the desired bright nickel thickness. The temperature and degree of agitation, as mechanical or air agitation, may be suitably adjusted for the particular bath composition and plating speed required. Temperatures of 40 to 60 (3., say 50 C., may normally be employed. The electrometric pH may preferably range from 3 to 5 and most preferably from 3.8 to 4.2. Cathode current densities may be adjusted to values which may be optimum for the particular bath concentration, temperature, and type of bath agitation involved, and generally may range between 2 and 12 amperes per square decimeter, say 4 a.s.d. in a nickel plating bath, say a Watlts-type bath as in Table I, supra. The deposit may be applied directly to the basis metal or over an intermediate coating of semibright nickel, copper, bronze, brass, etc.

Best plating results are usually achieved in the electrodeposition process when there is used a method of preventing the thin film immediately adjacent to the cathode from becoming depleted in cation content. This is desirably accomplished by agitation such as by air agitation, solution pumping, moving cathode rod, etc. With increasing agitation a lower concentration of primary brightener may advantageously be used.

With suitable choice of cooperating additives, deposits of high luster, leveling, ductility and excellent chromium receptivity may be obtained. Since the secondary brighteners of this invention may be relatively stable to hydrolysis, oxidation or reduction, only very infrequent purification treatments may be necessary (such as activated carbon treatment) to maintain adequate deposit ductility.

The following illustrative examples disclose synthesis of typical additives of this invention. All parts are by weight except where otherwise indicated.

Example 1 To a magnetically stirred methanol solution (1200 parts) solution of 180 parts (3.2 moles) of potassium hydroxide and 201 parts (1 mole) of orthosulfonamidobenzoic acid. there may be added slowly, over a period of 15 minutes, a solution of 385 parts (3.2 moles) of 1,3-propane sultone in 400 parts of methanol. During this addition, carried out under reflux, the temperature rises rapidly almost to boiling. The reaction mixture may then be heated under reflux for about 4 hours and then cooled. The white precipitate formed may be filtered, washed several times with ether and then dried in an oven at 116 C. (for 1 hour). The product, potassium 3-sulfopropyl-ortho-[N,N-(potassium 3-sulfopropyl)] sulfonamidobenzoate may be obtained in substantially quantitative yield.

The product may then be dissolved in water to give an g./l. solution which may also be used as a convenient stock solution to make additions to the nickel plating bath both for make-up and replenishment.

Example 2 Substantially quantitative yield of sodium 3-sulfopropyl-ortho[N-(sodium 3-sulfopropyl] sulfonimido benzoate may be prepared as under Example 1 but using 84 parts (2.1 moles) of sodium hydroxide, 201 parts (1 mole) of o-sulfonamidobenzoic acid, and 256 parts (2.1 moles) of 1,3-propane sultone as reactants. The product may be isolated and formulated as a stock solution as under Example 1.

Example 3 Substantially quantitative yield of sodium 3-sulfopropyl-orthosulfonamidobenzoate may be prepared as under Example 1 but using 42 parts (1.05 moles) of sodium hydroxide, 201 parts (1 mole) of o-sulfonamidobenzoic acid, and 128 parts (1.05 moles) of 1,3-propane sultone as reactants. The product may be isolated and formulated as a stock solution as under Example 1.

The following illustrative examples, 4-23, disclose the effect of the use of the additives of this invention in formulating electroplating baths and in processes for bright nickel plating.

In Examples 4 to 15 the following typical Watts bath composition may be used:

G./l. Nickel sulfate 300 Nickel chloride 60 Boric acid .I 45

Mechanical and/or air agitation may be employed in each example. For mechanical agitation 0.5 g./l. of a highly pure grade of sodium lauryl sulfate or equivalent may be added. For air agitation, 0.25 g./l. of sodium din-hexyl sulfosuccinate or equivalent may be added. Cathodes may be polished brass suitably cleaned as per usual electroplating practice before being bright nickel plated. The anodes may be SD nickel.

Secondary brighteners, secondary auxiliary brighteners and primary brighteners employed may be indicated by the code letters below, in all of the following examples.

In all of the following examples, except where indicated differently, bright, ductile, Well-leveled deposits may be obtained.

Secondary brighteners Secondary auxiliary brighteners (F) Sodium allyl sulfonate. (G) Sodium 3-chlorobutene sulfonate-l. (H) Sodium butene-diol-1,4-sulfonate-3.

Primary brighteners (I) N-( 1,2-dichloropropenyl) pyridinium chloride.

(J) N-(l-propyne) 2,4,6 trimethyl pyridinium bromide.

(K) 1-diethylamino-2-propyne.

(L) l-dimethylamino-Z-propyne.

(M) Bis(beta hydroxy ethyl ether) of 2-butyne-l,4- diol.

(N) 2-hutyne-1,4-diol.

(O) 3,4,4-tri-beta-cyanoethyl-thio-hydantoin.

Zinc Cathode pH Temp., G./l. Tolerance Current Electro- C.

Density metric ina.s.d.

Hull Cell Zinc. Current Temp., G./1. Tolerance Density pH C. Range in a.s.d.

Example 14:

D No.; 0-12 4. 0 55 Description of Plato: Poor coverage,

dark and striated deposits in low current density end of range.

In Examples 16-19 the utility of the compounds of this invention in the following high chloride system is illustrated:

Nickel chloride 250 Nickel sulfate 250 Boric acid Cathode GJl. Zinc Current pH Temp.,

Tolerance Density C.

in a.s.d.

4 3. 2 }No 5 4. 0 I-.. 0.020 Example 17:

Yes 5 4. 0 55 Description of Plate: Deposit not bright; extremely brittle.

In Examples 20 and 21 the utility of the compounds of this invention in a high chloride bath having the follow- The following examples illustrate the utility of the compounds of this invention in a snlfamate-type nickel plating bath having the following composition:

Nickel sulfamate 375 Nickel chloride 45 Boric acid 45 Cathode G./l. Zinc Current pH Temp,

Tolerance Density C.

in a.s.d.

As many embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention includes all such modifications and variations as come within the scope of the appended claims.

I claim:

1. A process for electroplating nickel onto a basis metal which comprises passing current from an anode to a basis metal cathode through an aqueous acidic nickel plating solution containing at least one nickel compound providing nickelions for electroplating nickel, a primary brightener, 'and as a secondary brightener, a suflicient amount of a compound containing an anion of the structure:

ooo-R-so3 'R SO 3 ia la ['R a]bHi-s wherein a and b are each integers 0-1 and R is a hydrocarbon-di-yl moiety which contains at least 2 carbon atoms.

2. A process as claimed in claim 1 for electroplating nickel onto a basis metal wherein a secondary auviliary brightener is also preesnt in said aqueous nickel plating solution 3. A process as claimed in claim 1 for electroplating nickel onto a basis metal wherein R in said secondary brightener is a polymethylene group (CH wherein n is an integer 2-5. I x

4. A process as claimed in claim 1 for electroplating nickel onto a basis metal wherein said secondary brightener contains an anion of the structure wherein a and b are each integers 0-1.

5. A process as claimed in claim 1 for electroplating nickel onto a basis metal wherein said secondary brightener contains an anion of the structure COO (0119380 S Oz-NH3 6. A process as claimed in claim 1 for electroplating nickel onto a basis metal wherein said secondary brightener contains an anion of the structure z)aSOF 7. A process as claimed in claim 1 for electroplating nickel onto a basis metal wherein said secondary brightener contains an anion of the structure 8. A nickel plating solution comprising an acetic aqueous nickel plating solution including at least one nickel compound providing nickel ions for electrodeposition of nickel on a basis metal cathode, a primary brightener, and as a secondary brightener, a sufficient amount of a compound containing an anion of the structure 7 [R-S Oa] bHl-b wherein a and b are each integers 0-1 and R is a hydrocarbon-di-yl moiety which contains at least 2 carbon atoms.

9. A nickel plating solution as claimed in claim 8 wherein a secondary auxiliary brightener is also present in said aqueous nickel plating solution.

10. A nickel plating solution as claimed in claim 8 wherein R in said secondary brightener is a polymethylene group (CI-I wherein n is an integer 2-5.

11. A nickel plating solution as claimed in claim 8 'wherein said secondary brightener contains 'an'anion of the structure C O O (CHzhSOg' wherein a and b are each integers 0-1.

12. A nickel plating solution as claimed in claim 8 wherein said secondary brightener contains an anion of the structure 13. A nickel plating solution as claimed in claim 8 wherein said secondary brightener contains an anion of the structure 14. A nickel plating solution as claimed in claim 8 wherein said secondary brightener contains an anion of the structure G. KAPLAN, Assistant Examiner. 

